Technology is improving rapidly, the Google test cars got into accidents mostly because of how shytty human drivers are in comparison, people just running into their test cars.
I wouldn't say Uber drivers are paid shytty, the average Uber driver makes $20 an hour, the problem is Uber doesn't pay for gas/insurance. They will bite the bullet on the front end and make the money back on the back end, driverless cars will be more efficient and wont have hours they can't work. I'd imagine they will initially replace the full time Uber drivers first, mainly because those are the people making the most money for them and getting paid the most.
They have drivers right now for testing purposes.
The technology is a few years away, Cali will no doubt allow them in the future.